The fineness and duration of grinding food waste are important considerations in the design and operation of a disposer. Many conventional food waste disposers use a single speed induction motor that rotates a grinding plate to grind food waste. The rotational speed of the grinding plate for most food waste disposers is between 1700 and 1800 rotations per minute (RPM). A food waste disposer having an induction motor is disclosed in U.S. Pat. No. 6,007,006 (Engel et al.), which is owned by the assignee of the present application and incorporated herein by reference in its entirety.
It has been found that the selected rotational speed of the grinding plate may affect the grind performance of the disposer for certain types of foods. For example, harder food particles such as carrot fragments and bone fragments may “ride” on the grinding plate at high rotational speeds. Riding occurs when food particles rotate at the same speed as the grinding plate without being ground. Riding results in increased noise and vibration, as well as, residual food left in the grinding chamber after the disposer is turned off. Over time, residual food may cause unpleasant odors. Thus, a need exists for a food waste disposer having a mechanism to ensure all food is removed from the grind chamber.
Reduced flow in drain pipes is another important consideration in the design of a food waste disposer. A grinding chamber of a food disposer may be filled with food before the disposer is turned on by the user. For example, a user may fill the grinding chamber with potato peels before activating the disposer. When the conventional food waste disposer is turned on and immediately directed to a high rotational speed, a large slug of food may be forced down the discharge or drainpipe. This may reduce drain flow. Thus, a food waste disposer is needed that can prevent a large slug of food waste from being forced down the drainpipe during startup.
Another area of concern with conventional disposers is noise and power consumption. The typical rotational speed of the grinding plate for conventional disposers is fixed at a relatively high speed. Higher rotational speeds may produce more noise and consume more power. There may be times where the disposer is not grinding food but still turned on and running. For example, if a user is cleaning off the dinner table, there may be times when the disposer is running but no food is in the disposer. It would be beneficial to reduce the speed caused during periods of inactivity. Thus, there is a need for a disposer that reduces speed and power consumption during times of inactivity.
A further problem in designing a food waste disposer is jamming. Food waste in a conventional food waste disposer is forced by lugs on a rotating grinding plate against teeth of a stationary shredder ring. Jamming occurs when hard objects such as bones enter the food waste disposer and get stuck between the lugs of the rotating grinding plate and the stationary shredder ring. The prior art has tried to solve jamming by using motors that can be manually switched to rotate in the opposite direction. There is a need, however, for a food waste disposer that can automatically correct itself if a jam has occurred.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the conditions set forth above.